Is helping a beneficial learning experience for red-cockaded woodpecker (Picoides borealis) helpers?

Several hypotheses have been suggested to explain the evolution and maintenance of helping behavior in cooperatively breeding birds, one of which we investigated in the red-cockaded woodpecker (Picoides borealis). Helping may provide a learning experience that improves reproductive success once the helper becomes a breeder. We used data collected from a population of red-cockaded woodpeckers in the Sandhills of North Carolina to compare the reproductive success of 2-year-old breeders that were helpers at age 1 (helping experience) to those that were floaters or solitary males at age 1 (no helping experience). Reproductive success of the two groups was similar, indicating that helping provides no experience useful in reproduction. We reject the learning experience hypothesis as an explanation for the maintenance of helping behavior in red-cockaded woodpeckers. Received: 29 July 1996 / Accepted after revision: 27 April 1997     

安徽省宣州扬子鳄饲养种群繁殖现状分析

对１９９３ ～１９９８ 年安徽省扬子鳄繁殖研究中心内的亲代与子代鳄的繁殖情况进行了统计研究,结果表明：扬子鳄亲代卵的平均受精率为（７５．６６±２．２９） ％ ,子一代为（６９ ．２４ ±５ ．１２） ％ ,经ｔ 检验,两者差异显著;亲代产卵孵化幼鳄的平均畸形率为（０．３０ ±０．２０） ％ ,而子一代产卵幼鳄平均畸形率为（１ ．８５±０．９５） ％ ,经ｔ 检验,两者差异显著．但受精卵幼鳄孵化率在两代间差异不显著．通过饲养种群的家系和有效群体大小分析,作者认为造成子代鳄的繁殖率下降和畸形率上升的原因与近亲繁殖有关．对扬子鳄的遗传保护研究提出了建议．     

Reproductive partitioning in communally breeding guira cuckoos,<Emphasis Type="Italic"> Guira guira</Emphasis>

Guira cuckoos, Guira guira, exhibit a rare polygynandrous reproductive system with groups containing several male and female breeders, allowing for important tests of reproductive skew models. Female reproductive strategies involve leaving the group, varying clutch size, egg ejection and infanticide, among others. Here we examined the predictions of reproductive skew models relative to reproductive partitioning among females in groups. We used yolk protein electrophoresis to identify individual females eggs in joint nests. We found that reproductive partitioning favors early-laying females, which lay and incubate more eggs than females that begin laying later. Because the female that lays first tends to switch between repeated nesting bouts, and females do not always contribute eggs to each bout, female reproductive success tends to equalize within groups over time. The pattern of reproductive partitioning differs from that described for anis, another crotophagine joint-nester. We calculated reproductive skew indices for groups in 2 years, for both laying and incubation, as well as an overall population value. These were compared to random skew generated by simulations. Varying degrees of skew were found for different groups, and also across sequential nesting bouts of the same groups. Overall, however, skew did not deviate from random within the population. Nests that reached incubation tended to have lower skew values during the laying phase than nests terminated due to ejection of all eggs followed by desertion. Groups had higher reproductive skew indices in their first nesting bout of the season, and these nests frequently failed. These results illustrate the importance of social organization in determining not only individual, but group success in reproduction, and highlight the flexibility of vertebrate social behavior.Communicated by J. Dickinson     

On the social structure of offspring rearing in the burrower bug,<Emphasis Type="Italic"> Sehirus cinctus</Emphasis> (Hemiptera: Cydnidae)

Maternal-offspring interactions are important in a variety of animals. Understanding the evolution of these interactions requires that we also study the broader social context in which they occur. To date, behavioral studies on burrower bugs, Sehirus cinctus, have focused exclusively on interactions between mothers and offspring. Here we ask whether these interactions occur in a social context that extends beyond the family unit of a mother and her own genetic offspring. Such social structure can arise from behaviors that occur before eggs are laid, or from actions of individuals that occur post-hatching. We present field data showing that lay sites of mothers are spatially aggregated on a scale that would lead to behavioral interactions among families. Microsatellite markers suggest neighboring mothers are unrelated. Laboratory experiments do not support the hypothesis that spatial aggregation results from a direct attraction of females to one another. Other laboratory studies reported here indicate that, after hatching, unrelated clutches sometimes join together to form multifamily groups. Experiments reveal that mothers are not necessary for these joining events to occur. In sum, these data suggest that both mothers and offspring play active, but different, roles in generating the social environment in which offspring rearing occurs.Communicated by N. Wedell     

Arrival timing and seasonal reproductive performance in a long-distance migratory landbird

The date when a landbird migrant arrives on its breeding grounds may have reproductive consequences. Generally, early arriving individuals begin breeding earlier and consequently experience greater seasonal reproductive performance. Here, we describe relationships between arrival timing and seasonal reproductive performance in the American redstart (Setophaga ruticilla), a long-distance passerine migrant, arriving at northerly breeding grounds in Michigans eastern Upper Peninsula. Evidence suggests that both males and females benefited from early arrival at the breeding grounds. Early males appeared to settle on higher quality territories and hatched nestlings sooner than later arrivals. Early females began their clutches early, produced heavier nestlings and possibly laid more eggs than later arrivals. Larger clutches and heavier offspring increase the likelihood of offspring recruiting into the breeding population. The findings of this study point to fitness consequences arising from when a bird arrives at its breeding grounds. These results also have implications for understanding how events occurring during spring migration influence reproductive performance as migratory delays likely influence arrival timing.Communicated by: W. Wiltschko     

王锦蛇的无冬眠饲养试验

2004年11月～2005年4月，进行了王锦蛇的冬眠期饲养试验．结果表明：在王锦蛇的冬眠期内，人工保持其环境温度为25～30℃，相对湿度为60％～85％，并提供其所需要的食物条件，就能够使王锦蛇在冬眠期内正常地生长发育，不仅能缩短其饲养时间，而且能提高其成活率，从而达到高效饲养王锦蛇的目的．     

化学诱变结合结构类似物法选育高苯丙氨酸解氨酶菌种

ＥＭＳ诱变结合结构类似物法提高含ＰＡＬ出发菌株红酵母Ｒｈｏｄｏｔｏｒｕｌａ ｓｐ．ＣＩＢＡＳＡ１４０１１００ 生物转化能力阳性率为３５．５ ％ ,部分突变株ＰＡＬ转化能力提高１ 倍以上,其中Ｅ１０５,Ｅ２４０ 具有快速转化能力,反应３ ｈＬＰｈｅ累积浓度达到１ ｇＬ左右．φ１０％ 甘油和３０ ｇＬＧｌｕ 对ＰＡＬ转化具有明显的稳定作用．用含φ１０％ 甘油和３０ ｇＬＧｌｕ 的反应液进行生物转化制备,Ｅ１０５ 和Ｅ２４０ 在２４ ｈ 期间ＬＰｈｅ 质量浓度大于２０ ｇＬ,转化率达８０ ％ ．     

Plasma levels of androgens and gonadal development of breeders and helpers in the bell miner (Manorina melanophrys)

Plasma concentration of androgens and gonad development were studied in wild cooperatively breeding bell miners (Manorina melanophrys) of different age, sex and social status. Plasma levels of androgens increased with age of birds. For sexually mature (SM) bell miners, androgen levels were higher in breeders than in nonbreeding (NB) helpers (P < 0.005), and they were marginally higher in females than in males (P < 0.10). Thus female breeders showed the highest plasma levels of androgens. This pattern may be explained by an asymmetry between the sexes in the levels of competition needed to reach and defend breeding status; the degree of intra-sexual competition seems to be higher among female bell miners than among males. In general, male breeders had larger gonads than male SMNB helpers; male breeder gonads produced spermatozoa whereas most helpers' gonads did not. However, old (i.e. 34 months) SMNB male helpers had large gonads producing spermatozoa in spite of having low plasma levels of androgens. We suggest that young male bell miners may be under a voluntary mechanism of reproductive suppression perhaps favoured by inbreeding avoidance; although some aggressive interactions observed between very young helpers (about 2 months) and adult members of the breeding unit suggests that a certain degree of imposition also occurs at young ages. Older male helpers may avoid aggression with the male breeder and imposed reproductive suppression, hence the low circulating levels of androgens, but they have the potential to sneak extra-pair copulations. Gonad size decreased during the non-breeding season in both sexes.     

Costs and benefits of communal rearing to female prairie voles (<Emphasis Type="Italic">Microtus ochrogaster</Emphasis>)

Communal rearing of offspring may help mothers maximize their investment in offspring at a reduced cost to their own bodily condition, thus maximizing their potential for reproductive success. The objective of this study was to quantify the costs and benefits of communal rearing to prairie vole (Microtus ochrogaster) pups and mothers. Mothers were assigned to one of three social units: solitary mothers, singularly breeding groups (i.e. one mother and one non-reproductive sister) and plurally breeding groups (i.e. two lactating sisters). For each type of social unit, some replicates were provided with food ad libitum, while others were provided with limited food. The body mass of focal mothers (i.e. the first mother to produce a litter) was a significant predictor of pup growth. Regardless of food availability, litters of focal mothers in plurally breeding groups gained more weight than litters reared by solitary mothers. Pups reared in singularly breeding groups were intermediate in weight gain, but did not gain significantly more weight than solitary offspring. There was no difference in the body mass of focal mothers from each type of social unit, regardless of food availability. Within plurally breeding groups, the weight gain of the two litters and body mass of focal and second mothers did not differ. However, focal mothers from plurally breeding groups nursed fewer pups than solitary mothers and also fewer pups than their nestmates when food was limited. Our results suggest that plural breeding results in greater fitness to mothers than solitary and singular breeding.Communicated by E. Korpimäki     

Experimental evidence for helping and hindering by previous offspring in the cooperative-breeding Seychelles warbler Acrocephalus sechellensis

Prebreeding Seychelles warblers (Acrocephalus sechellensis) frequently act as helpers on their natal territory, aiding in territory defence, predator mobbing, nestbuilding, incubation (only females) and feeding dependent young of their parents. In some cases helpers could attain breeding status (e.g. by joint-nesting) in their natal group and become co-breeders. Comparisons of group size and reproductive success on a given quality territory suggest that the presence of alloparents (helpers and cobreeders) significantly affects the reproductive success of their parents. The influence of alloparents on reproductive success was examined by removing alloparents from breeding units and comparing the success of natural-sized and artificially reduced groups. Removal experiments, controlled for territory quality, group size and breeder age, showed that the presence of one alloparent significantly improved the reproductive success of its parents. Analysis strongly suggests that this was entirely due to helping behaviour (i.e. providing care to offspring of their parents), thereby improving the helper's inclusive fitness benefits from staying at home. However, these experiments showed also that the presence of two or more alloparents in medium-quality territories significantly decreased reproductive success, compared with groups with one alloparent. Several lines of evidence suggest that this may have been due to the joint-nesting and reproductive competition that could occur in breeding groups, or simply to resource depression when a large number of previous offspring remained on their natal territory.